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Determining the exact reason for its spike in popularity is difficult, but seltzer has a few qualities that make it attractive. The most obvious reason is that the beverage is sugar-, salt-, and calorie-free.

As the American public weans itself off sugary drinks, it seems to be searching for a replacement.

Diet soda is waning in popularity even more than full-calorie soda. For years, low-calorie sodas with artificial sweeteners have been the choice of those watching their weight. Now research suggests that artificial sweeteners may increase people’s appetites and make weight loss even more difficult.

A study published in The Lancet showed that aspartame consumption increased people’s appetites more than plain water. This means that drinking a diet soda gives you fewer direct calories, but it increases the likelihood that you’ll consume more calories from another source or sources after drinking it.

There have long been concerns about other negative effects of artificial sweeteners. A meta-analysis of studies on non-nutritive sweeteners found conflicting results about whether sweeteners were actively bad for the health or simply neutral. Note that no studies indicated artificial sweeteners have positive effects on body-mass index or cardiac health.

Because of this research, consumers are ditching diet sodas at high rates. In 2016, Diet Pepsi consumption fell 9.2 percent and Diet Coke fell 4.3 percent.

It’s not clear that these former customers are embracing sparkling water, but clearly there is a share of the beverage market up for grabs.

Seltzer is not quite plain water in terms of nutrition.

The appeal of seltzer is clear in light of the confusing data on sweeteners. Because seltzer has no sweeteners or sodium, there are fewer health concerns. Seltzer waters often have flavors added to them, but these are generally natural ingredients added in small quantities.

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It’s not all good news for seltzer water, though. Much like artificial sweeteners, there is evidence to suggest that the carbonation that is characteristic of seltzer water could increase your appetite.

There are also concerns that bubbly water could erode your tooth enamel—especially if the variety you select has citrus flavoring. Despite these concerns, experts agree that seltzer is far better for you than either regular or diet soda.

Millennials are embracing the bubbly drink.

Seltzer companies are finding a receptive audience in millennials through social media campaigns. Instead of television ads or magazine spreads, sparkling water company LaCroix focuses on Instagram.

The company uses hashtags, such as #LiveLaCroix, to find and interact with their customers. Those who pose with a can of brightly colored LaCroix could find themselves featured on LaCroix’s Instagram page, which has more than 100,000 followers.

The gaudy colors of LaCroix cans make them perfect for featuring in photos. But the additive-free sparkling water found within those artsy cans is what really spurred the beverage’s rise to prominence.

Unless researchers uncover major health risks with carbonation, we expect seltzer water to keep growing in popularity.